Na+, K+ and water balance in young spontaneously hypertensive rats: relationship to blood pressure after high K+ treatment

1. These studies were designed to investigate the effects of high dietary K+ on electrolyte and water balance in young spontaneously hypertensive rats (SHR) and to relate these effects to changes in blood pressure. 2. The high K+ diet reduced blood pressure by approximately 10 mmHg during the development of hypertension. Blood pressure, however, plateaued at the same maximum level as control by age 13 weeks. 3. Rats fed the high K+ diet showed a significant increase in water intake and urine volume throughout the treatment period but no change in plasma volume or extracellular fluid volume occurred. 4. A slight natriuresis was also observed in rats on the high K+ diet, but this was not of sufficient magnitude to decrease total body Na+. 5. These results confirm previous findings that K+ causes a diuresis and a natriuresis, but demonstrate that the diuretic action of K+ cannot explain its antihypertensive properties in young SHR.

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Effects of a high K+/low Na+ diet on blood pressure in young spontaneously hypertensive rats

Clinical Science ◽

10.1042/cs0720313 ◽

1987 ◽

Vol 72 (3) ◽

pp. 313-319 ◽

Cited By ~ 3

Author(s):

A. Louise Sugden ◽

James A. Straw ◽

Barbara L. Bean

Keyword(s):

Blood Pressure ◽

Plasma Renin Activity ◽

Water Intake ◽

Mechanism Of Action ◽

Spontaneously Hypertensive Rats ◽

Urine Volume ◽

Plasma Renin ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

High K

1. Blood pressure was measured after treatment with a high K+, a low Na+ and a combined high K+/low Na+ diet in young spontaneously hypertensive rats (SHR). 2. A high K+ diet reduced blood pressure by approximately 10 mmHg during the development of hypertension. This decrease was accompanied by a significant increase in water intake and urine volume and a significant decrease in plasma renin activity (PRA). 3. A low Na+ diet also decreased blood pressure significantly, but, in contrast to the high K+ diet, water intake and urine volume significantly decreased and PRA increased. 4. When both diets were given together, the antihypertensive effects of both were eliminated. Thus while an increase in dietary K+ and a decrease in dietary Na+ are both effective antihypertensive regimens in SHR, the mechanism of action of each appears to be different and may be antagonistic in these animals.

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High-potassium diet attenuates salt-induced acceleration of hypertension in SHR

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.260.1.r21 ◽

1991 ◽

Vol 260 (1) ◽

pp. R21-R26 ◽

Cited By ~ 2

Author(s):

Y. Sato ◽

K. Ando ◽

E. Ogata ◽

T. Fujita

Keyword(s):

Blood Pressure ◽

Renal Function ◽

Spontaneously Hypertensive Rats ◽

Hypertensive Rats ◽

High Potassium ◽

Spontaneously Hypertensive ◽

Antihypertensive Action ◽

High K ◽

Wistar Kyoto ◽

Renal Vascular

We studied the effects of K supplementation (8% KCl) for 4 wk on blood pressure (BP), Na space, and renal hemodynamics in 5-wk-old, spontaneously hypertensive rats (SHR) or age-matched Wistar-Kyoto rats (WKY) eating normal-NaCl (0.66%) or high-NaCl (8%) diet. In WKY, high-Na and/or high-K diets had no effects on BP. In SHR, Na load accelerated the development of hypertension, whereas K supplementation did not affect BP of normal-Na SHR but attenuated the increase in BP with Na load. Correspondingly, Na load in SHR significantly increased renal vascular resistance (RVR), and K supplementation attenuated the increased RVR of Na-loaded SHR. Moreover, Na space of SHR was increased compared with that of WKY, and although Na load did not affect Na space, K supplementation tended to decrease Na space in SHR. These results indicate that 9-wk-old SHR is relatively volume-expanded compared with age-matched WKY, and K supplementation could improve the lowered slope of the pressure-Na excretion relationship in SHR, resulting in maintenance of Na balance. Thus the data suggest that changes in RVR, which might be intimately related to renal function for Na excretion, contribute to both salt sensitivity of SHR and antihypertensive action of K supplementation in Na-loaded SHR.

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Effects of diuretics on stroke development in Kyoto–Wistar stroke-prone spontaneously hypertensive rats

Clinical Science ◽

10.1042/cs0810335 ◽

1991 ◽

Vol 81 (3) ◽

pp. 335-340 ◽

Cited By ~ 7

Author(s):

John S. Smeda ◽

Olexa Tkachenko

Keyword(s):

Blood Pressure ◽

Untreated Control ◽

Spontaneously Hypertensive Rats ◽

Haemorrhagic Stroke ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

High K ◽

Blood Pressures ◽

Low K

1. Previous studies have indicated that increases in dietary K+ promote diuresis and retard stroke development in stroke-prone spontaneously hypertensive rats (spSHR) fed a Japanese-style diet containing 4% NaCl. 2. It is possible that elevations in dietary K+ retard stroke development by inducing natriuresis and facilitating the clearance of Na+, and that diuretics associated with natriuresis might also be capable of retarding stroke development in spSHR. To test if this was the case, the onset of stroke development in spSHR fed a low (0.75%) K+ diet containing 4% NaCl (controls) was monitored and compared with that in spSHR treated with (a) frusemide, (b) chlorothiazide, (c) amiloride or (d) acetazolamide, and with (e) untreated spSHR fed a high (2.11%) K+ diet. 3. The onset of stroke, as well as death resulting from stroke, occurred at a significantly later age in spSHR fed a high K+ diet than in spSHR fed a low-K+ diet, despite the fact that both groups of spSHR rats had comparable blood pressures. 4. Treatment of spSHR with the above-named diuretics before stroke development did not alter the blood pressure of the rats. The onset of stroke development and death in spSHR treated with chlorothiazide, amiloride or acetazolamide was comparable with that observed in untreated control spSHR. In spSHR treated with frusemide, the onset of stroke was comparable with that of untreated control spSHR, whereas the onset of death after stroke development was accelerated. 5. Post mortems performed on spSHR that developed stroke indicated the presence of haemorrhagic stroke of comparable severity in the six groups of spSHR studied. 6. The results indicate that treatment of spSHR with diuretics at levels which do not alter the animals’ blood pressure does not alter the timing or incidence of stroke development, and does not prolong the lifespan of the animals after stroke has developed.

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The effects of hydrogenated coconut oil, safflower oil, and evening primrose oil on development of hypertension and sodium handling in spontaneously hypertensive rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y85-059 ◽

1985 ◽

Vol 63 (4) ◽

pp. 325-330 ◽

Cited By ~ 22

Author(s):

Masayoshi Soma ◽

Mehar S. Manku ◽

David F. Horrobin

Keyword(s):

Blood Pressure ◽

Spontaneously Hypertensive Rats ◽

Urine Volume ◽

Coconut Oil ◽

Safflower Oil ◽

Evening Primrose Oil ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Evening Primrose ◽

Sodium Handling

Spontaneously hypertensive rats (SHR) were fed a basal regular diet (BD) or three different fat supplemented diets which contained 10% hydrogenated coconut oil (HCO), 10% safflower oil (SFO), or 10% evening primrose oil (EPO). The rats received these four different diets from 4 weeks to over 24 weeks of age. The development of hypertension in SHR was significantly retarded in the EPO-supplemented animals. The blood pressure was lower in the SFO group animals as compared with the BD and HCO groups, but this did not reach significance. Sodium excretion rate in young SHR was increased in the EPO group compared with the HCO and SFO groups, and the urinary K/Na ratio was decreased in the EPO group compared with the HCO and EPO groups. Water intake and urine volume were increased in the SFO group as compared with the HCO and EPO groups. Sodium concentration in erythrocytes was decreased in the rats receiving SFO. Pressor responses to norepinephrine and angiotensin II were enhanced in the EPO and SFO groups as compared with the basal chow group. These data suggest that a dietary supplementation of EPO which contains a substantial amount of gamma-linolenic acid consistently lowers blood pressure in SHR. The mechanism is uncertain, but the effects on sodium handling may in part be responsible for the retardation of the development of hypertension. There was a difference between the EPO and the SFO groups in sodium–water handling, and to some extent in the blood pressure development in SHR.

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